This invention relates to a liquid crystal display device and relates to a liquid crystal display device in which there is little color change even if there is environmental variation, there is little color changes even when the angle at the time of viewing changes, contrast is high, and there is little variation in visibility due to stretch spots.
There have been various requirements for the polarizing plate protective film used for the polarizing plate as a result of high performance and high definition liquid crystal devices. Of course, it is required, for example, to be durable in the sense that the properties of the polarizing plate protective films do not deteriorate with extended use, and to have excellent uniformity so that the properties do change under harsh environmental conditions.
An optical compensation film is used in order to expand the viewing angle of the liquid crystal display device, and examples of the materials used therefore include norbornene, polycarbonate, polysulfon, polyether sulfon, amorphous polyolefin and the like. In order to use these polymerized optical compensation films in combination with polarizing plates, they are generally adhered, and there is the disadvantage that there is a large number of laminated films and the cost is high. In addition to the fact that the manufacturing process is complex, there is a problem in that defective products are generated because at the time of adhesion, bubbles or foreign material are introduced and this causes wrinkling or the like.
To solve these problems, it is known that the optical compensation film which has cellulose resin as the main material can be adhered to the polarizing plate instead of the polarizing plate protective film, and as a result the manufacturing process for the polarizing film is shortened and production efficiency is excellent (See Patent Documents 1-5) for example.
In particular, in Patent Document 6, technology is disclosed in which a TAC film that has been manufactured by liquid casting is used, and a polymer layer is coated onto a film support and a desired phase difference is imparted by stretching the support at a high temperature and then the polarizing plate is adhered. However, although this technology has various excellent features as an optical compensation film, when the color changes due to environmental variation and visibility due to stretch spots are considered, it is clear that when the screen brightness is adjusted in accordance with the surrounding brightness at the time of image viewing in particular, there are changes in visibility such as contrast and color shifts.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-71957 Publication
[Patent Document 2] Japanese Patent Application Laid-Open No. 2002-62430 Publication
[Patent Document 3] Japanese Patent Application Laid-Open No. 2001-249223 Publication
[Patent Document 4] Japanese Patent Application Laid-Open No. 2002-82226 Publication
[Patent Document 5] Japanese Patent Application Laid-Open No. 2002-98832 Publication
[Patent Document 6] Japanese Patent Application Laid-Open No. 2004-4474 Publication